Lubricant-Free Compressor Having a Graphite Piston in a Glass Cylinder

ABSTRACT

A substantially lubricant-free compressor comprising a glass cylinder having a hollow interior, a graphite piston within the glass cylinder, a connecting rod operably attached to the graphite piston, a cylinder head sealing one end of the glass cylinder, an exhaust valve in operable connection with the hollow interior of the glass cylinder, and an inlet valve in operable connection with the hollow interior of the glass cylinder. The compressor may be driven by any suitable means including without limitation a brushless DC motor or a smart material actuator.

RELATED APPLICATIONS

This application is a non-provisional application based upon, and claims benefit of, U.S. Provisional Application No. 61/723,815, filed Nov. 8, 2012, which is hereby incorporated by reference in its entirety.

BACKGROUND

The present invention relates in general to the field of gas compressors. Compressors are known in the art. However, such compressors do not operate without a lubricant by utilizing a graphite piston in a glass cylinder. The present invention provides embodiments of compressors with several advantages over the prior art including improved transportability, reduced size, reduced power consumption, operation with little or no lubrication, and increased operational life.

This application hereby incorporates by reference U.S. Publication Numbers 2011-0309721; 2012-0038245; 2013-0234562; 2013-0234561, U.S. patents:

U.S. Pat. No. 7,564,171

U.S. Pat. No. 6,717,332;

U.S. Pat. No. 6,548,938;

U.S. Pat. No. 6,737,788;

U.S. Pat. No. 6,836,056;

U.S. Pat. No. 6,879,087;

U.S. Pat. No. 6,759,790;

U.S. Pat. No. 7,132,781;

U.S. Pat. No. 7,126,259;

U.S. Pat. No. 6,870,305;

U.S. Pat. No. 6,975,061;

U.S. Pat. Nos. 7,368,856; and 6,924,586. All incorporated patents, patent applications and patent publications are incorporated in their entirety.

BRIEF DESCRIPTION

Embodiments of the present invention provide a compressor with a glass cylinder having a hollow interior. A graphite piston is situated within the glass cylinder, with a connecting rod attached to the graphite piston. A cylinder head seals one end of the glass cylinder and has at least one exhaust valve in operable connection with the hollow interior of the glass cylinder. At least one inlet valve is in operable connection with the hollow interior of the glass cylinder. In certain embodiments, the inlet valves are mounted within the cylinder head. In other embodiments, the inlet valves are mounted on the graphite piston. Inlet and exhaust valves may also be situated in connection with lines connected to the compressor where a simpler cylinder head design is desirable.

Upon the connecting rod moving the graphite piston toward the cylinder head, material within the hollow interior of the glass cylinder is compressed. When a sufficient pressure is attained, a portion of the material is expelled out the exhaust valve. Upon the connecting rod moving the graphite piston away from the cylinder head, pressure within the glass cylinder is reduced and the exhaust valve substantially prevents backflow. The reduced pressure, however, allows material to be drawn into the hollow interior of the glass cylinder through the inlet valve. Repeated transverse movement of the graphite piston thereby serves to provide a supply of compressed material through the exhaust valve. Due to the low coefficient of friction between the graphite piston (and in some embodiments a low friction ring) and the glass cylinder, the need for lubrication is reduced or eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features in the invention will become apparent from the attached drawings, which illustrate certain embodiments of the apparatus of this invention, wherein

FIG. 1 is an example of a compressor assembly of the present invention with the glass cylinder shown in cross section to expose interior portions of the compressor;

FIG. 2 is a cross-section view of the embodiment illustrated in FIG. 1;

FIG. 3 is an exploded perspective view the embodiment illustrated in FIG. 1;

FIG. 4 is a cross-section view of an alternate embodiment of a compressor according to the present invention in which the inlet valve is mounted on the graphite piston;

FIG. 5 is a perspective view of the piston assembly of the embodiment illustrated in FIG. 4;

FIG. 6 is a perspective view of certain components of a cylinder head assembly suitable for use with the embodiment shown in FIG. 4;

FIG. 7 is a perspective view of the cylinder head of the embodiment illustrated in FIG. 1;

FIG. 8 is an alternate perspective view of the cylinder head of the embodiment illustrated in FIG. 1;

FIG. 9 is an exploded perspective view of an embodiment of a compressor according to the present invention having an electric motor and utilizing at least one low friction ring on the graphite piston; and

FIG. 10 is a perspective view of an embodiment of a compressor according to the present invention in which the glass cylinder is shown in cross-section and in which a smart material actuator is operably connected to the connecting rod driving the graphite piston.

DETAILED DESCRIPTION

While the following describes embodiments of this invention, it is understood that this description is to be considered only as illustrative of the principles of the invention and is not to be limitative thereof, as numerous other variations, all within the scope of the invention, will readily occur to others.

The term “adapted” shall mean sized, shaped, configured, dimensioned, oriented and arranged as appropriate. Herein, it will also be understood that in the figures, different embodiments may comprise the same or similar components. Where the same components are used in different embodiments, the same reference number may be used. Where components in different embodiments have a comparable structure, but are not necessarily common or identical parts, a similar number is used, but with a differing initial first digit, but common second and third digits. For example, and without limitation, cylinder heads 140, 240, 540, and 640 are examples of similar structures adapted for use in different embodiments of compressors 100, 200, 500, 600 of the present invention, but need not be interchangeable parts.

The various embodiments of the present invention for gas compression may be applicable to various operations used in numerous industries. For example, certain compressor embodiments may be utilized to pump air through a nitrogen filter in order to provide nitrogen. The nitrogen may be used for many purposes, including food refrigeration and preservation. In one embodiment, nitrogen may be fed to a vegetable drawer.

Embodiments may be utilized to compress refrigerant for a personal cooling device. Such an embodiment may be adapted for a soldier. An evaporator may be carried near the compressor in a neck pad or vest in contact with the soldier's body.

Certain embodiments may be utilized to pump air through a filter in order to scavenge oxygen. The generated oxygen may be provided to a person for health reasons or to assist in high-altitude activities, such as skiing. Other embodiments may be used to inflate bladders in vehicle seats or to drive tools and machines.

Embodiments of the compressor may be used with an electric motor or an actuator, which may operate at resonance. A brushless DC motor may be preferred for embodiments that need to operate at slower speeds. Such motors may be suitable for use with compressors having passive valves, such a reed valves. Resonant Piezo drive systems may operate at higher frequencies and may optionally use actively actuated valves. A brushless DC motor may be lower cost alternative. Additionally, other DC or AC motors can be used for such applications, such as conventional brushed motors.

An embodiment of the present invention comprises a compressor assembly that utilizes a glass cylinder with a graphite piston. The glass cylinder preferably comprises borosilicate glass such as Pyrex, but may also be formed of tempered glass, or other variations of glass materials known in the art that have thermal characteristics similar to those of Pyrex. An advantage of such an assembly is that the compressor may operate with minimal or zero lubricant, such as oil or grease. The lack of a lubricant in the compressor avoids contamination of the compressed gases. Contaminants into the air stream of lubricated compressors may include excessive oil vapor and carbon monoxide. Such impurities in the exiting gases may be harmful, especially if the gases are expected to be inhaled, and may require filtering before use.

Another advantage of the disclosed invention is the small size and light weight of the compressor. Accordingly, embodiments may be easily carried by a user. Transportability may be a critical feature for compressors that are intended to be carried by ill, weak or elder users that require an oxygen supply. Such compressors provide mobility without the burden of transporting heavy oxygen tanks. The compact size of certain embodiments allows the compressors to be used by skiers and soldiers.

Yet another advantage includes the low energy consumption of the compressor. Embodiments used with actuators may also operate at resonance to provide additional efficiencies.

FIG. 1 illustrates an embodiment of the present invention that comprises a compressor 100 utilizing a glass cylinder 110 with a graphite piston 120. While the piston may be of any convenient graphite material, fine-grained graphite is often suitable because of its strength and performance characteristics. The graphite piston 120 traverses a length of the glass cylinder 110 within the hollow interior of glass cylinder 110. Graphite piston 120 is operably attached to connecting rod 130 which may in turn be attached to a movement means (not illustrated) adapted to repeatedly urge graphite piston 120 back and forth in a transverse motion within glass cylinder 110.

Cylinder head 140 seals against on end of glass cylinder 110 with upper seal 146 (shown in FIG. 2) creating a seal. Upper seal 146 may be any suitable material for forming a substantially airtight seal between cylinder head 140 and class cylinder 110. Without limitation rubber and silicone such as are commonly used in the manufacture of gaskets are examples of suitable materials for upper seal 146. Fasteners such as bolts (not illustrated in FIG. 1) may conveniently pass through holes around the perimeter of cylinder head 140 to a base (not illustrated) in order to apply a clamping pressure against upper seal 146.

Cylinder head 140 has at least one outlet 160 through which compressed material may pass when compressor 100 is in operation. In the illustrated embodiment, inlet 150 and second inlet 152 are in operable connection with the hollow interior of glass cylinder 110 and enable material to flow into glass cylinder 110 when connecting rod 130 urges graphite piston 120 away from cylinder head 140. Whereas two inlets are shown in the illustrated embodiment, alternate embodiments of the present invention may include a single inlet or a plurality of inlets as needed to achieve the necessary flow characteristics for a given application.

Lower seal 170 partially seals glass cylinder 110 but allows connecting rod 130 to move freely during compressor operation. Where fully sealed operation is required (such as when compressing caustic materials) a bellows (not illustrated) can be used to provide a movable seal between connecting rod 130 and glass cylinder 110.

Cylinder head 140 may be formed of any material capable of withstanding the pressure and thermal constraints of the desired compressor application. Without limitation, steel, aluminum, brass and stainless steel are examples of suitable materials.

Referring to FIG. 2, it can be seen that exhaust valve 161 may conveniently be mounted in cylinder head 140 with the use of valve retaining plate 144. It can further be seen that connecting rod 130 may conveniently be operably attached to graphite piston 120 with piston T-nut 125 and spacer 127, each adapted to retain graphite piston 120 to connecting rod 130.

Referring to FIG. 3, inlet valve 151 and second inlet valve 153 are situated below inlet 150 and second inlet 152 respectively, and are held in place with valve retaining plate 144, which may conveniently be secured to cylinder head 140 with fasteners 145. Similarly, exhaust valve 161 may conveniently be situated beneath outlet 160 and also retained in position by valve retaining plate 144.

While a variety of valves may be used, including both passive valves and actuated valves, the illustrated embodiment shows inlet valve 151, second inlet valve 153, and exhaust valve 161 as passive reed valves. Upon connecting rod 130 moving graphite piston 120 toward cylinder head 140, pressure is asserted on material within glass cylinder 110. When such pressure reaches a point higher than the back pressure at outlet 160, and the difference is sufficient to operate exhaust valve 161, exhaust valve 161 opens and a portion of the material is expelled out exhaust valve 161. Upon connecting rod 130 moving graphite piston 120 away from cylinder head 140, pressure within glass cylinder 110 is reduced. Exhaust valve 161 then closes to prevent back flow from outlet 160. Inlet valve 151 and second inlet valve 153 open to allow additional material to be drawn in through inlet 150 and second inlet 152. When graphite piston 120 reverses, the increase in pressure closes inlet valve 151 and second inlet valve 153 and opens exhaust valve 161 as discussed above.

As has been noted, the location, configuration and number of inlets and exhausts can be varied according the needs of a particular application. In certain embodiments it may also be convenient to locate inlet and/or exhaust valves in lines connected to the compressor as opposed to in the cylinder head or piston assembly, as will be apparent to those of skill in the art.

FIG. 4 shows compressor 200, another preferred embodiment of a compressor according to the present invention. In the illustrated embodiment, cylinder head 240 comprises a single outlet 260. Valve retaining plate 244 captures exhaust valve 261 in cylinder head 240 such that exhaust valve 261 is in operable connection with the hollow interior of glass cylinder 210.

Graphite piston 220 is secured by piston T-Nut 225. Inlet valve 251 is mounted in piston T-Nut 225. Inlet 250 allows material to flow through graphite piston 220 and through inlet valve 251 into the hollow interior of glass cylinder 210.

It can further be seen in this figure how clamping plate 241 may be adapted to compress cylinder head 240 against glass cylinder 210 through the use of clamping fasteners 242 which may attach to a base (not illustrated) to allow clamping pressure to be exerted. Thus it is seen that clamping plate 241 may clamp against cylinder head 240 in this embodiment. Other embodiments may also conveniently include an integral extension (not illustrated on FIG. 4) to allow the cylinder head to accept fasteners 242 without the use of clamping plate 241.

FIG. 5 further illustrates the piston assembly of compressor 200. Graphite piston 220 has T-Nut 225 (illustrated on FIG. 4) which includes valve retaining plate 244 fastened thereto to secure inlet valve 251.

FIG. 6 illustrates components of an alternate embodiment of a cylinder head suitable for use with compressor 200. Cylinder head 340 comprises two exhaust valve seats 369 for receiving exhaust valves 361 and 363. Exhaust retaining plate 367 secures exhaust valves 361 and 363, which are illustrated as passive reed valves.

FIGS. 7 and 8 further illustrate cylinder head 140 as shown in FIGS. 1-3. In this embodiment, one larger exhaust port 162 is in operable connection with exhaust valve seat 164. Inlet 150 and second inlet 152 allow the passage of material into compressor 100. Inlet valve seat 154 and second inlet valve seat 155 are in operable connection with inlet 150 and second inlet 152.

It will be understood by those of skill in the art that in the embodiments so far described, graphite pistons 120 and 220 form a suitable seal with glass cylinders 110 and 210 respectively. This may be accomplished by adapting graphite pistons 120 and 220 to have an outside diameter substantially equal to the inside diameter glass cylinder 110 and 210 respectively. The natural low friction properties of the graphite and the glass will then allow graphite pistons 120 and 220 to move transversely during operation, even with a seal tight enough to allow a significant degree of compression. Graphite and borosilicate glass are preferred materials both because of their coefficients of friction and because their thermal characteristics are such that an operable seal can be maintained during compressor operation.

It should be noted, however, that it is not necessary to have tight tolerances between the graphite piston and glass cylinder. Referring to FIG. 9, one or more low friction ring 521 may be used to create the desired seal. While a single split ring can be used, having two or more split rings enable the openings to be offset to promote better sealing between low friction ring 521 and class cylinder 510. Utilizing a low friction material such as a synthetic resin (for example, and without limitation, such as Teflon) for split ring or rings forming low friction ring 521 allows reliable and prolonged used without the need for tight tolerances between the outside diameter of the graphite piston and the glass cylinder. Graphite is still preferred for the piston, however, due to its thermal characteristics.

Compressor 500 thus comprises cylinder head 540, glass cylinder 510, graphite piston 520 and low friction ring 521. Connecting rod 530 is operably connected to graphite piston 520 as has been previously described, and extends into housing 580. When assembled, lower seal 570 forms a seal against housing 580.

Compressor 500 also incorporates a means of generating transverse motion of graphite piston 530 comprising motor 585, eccentric 587, and shaft retainer 588. Motor 585 may be any motor, but is preferably an electric motor and more specifically is preferably a brushless DC motor. Motor 585 engages eccentric 587 substantially in the center of eccentric 587. Eccentric 587 comprises offset eccentric shaft 589 which is adapted to engage connecting rod bearing 531, which is retained by shaft retainer 588. As eccentric 587 rotates, offset eccentric shaft 589 imparts a substantially linear motion to graphite piston 520 through connecting rod 530.

FIG. 10 illustrates an alternative embodiment of compressor 600 according to the present invention, with an alternate motion generating means. As is further described in the incorporated references, and in particular in U.S. Published applications 2013-0234561 and 2013-0234562, smart material actuator 685 is mounted to compressor base 680, preferably with an actuator clamping plate (not illustrated) that clamps compensator 694 against compressor base 680. Upon application of a suitable electric potential to piezoelectric or smart material device 690, piezoelectric or smart material device 690 expands. That expansion results in flexing of webs 691 which transfer motion to actuating arms 692. Actuating arms 692 are operably connected to second stage connecting elements 693, which in turn transfer motion to second stage block 687. Second stage block 687 is operably connected to connecting rod 630, through which graphite piston 620 is moved. By repeatedly activating and deactivating smart material actuator 685, compressor 600 can thus be operated.

For certain high speed applications, it may be desirable to operate smart material actuator 685 at resonance. As is further described in incorporated U.S. Published application number 2012-0038245, resonant operation can be achieved using a control circuit (not illustrated) capable of operating smart material actuator 685 at a resonant frequency and adjusting the electric potential applied to smart material device 690 when resonance is achieved to prevent over-extension of webs 691. The result is a high frequency operation with reduced power consumption. It should be noted, however, that the configuration of base 680 can affect the resonant characteristics of the system. Accordingly different base and/or mounting means (not illustrated) may be used to achieve the desired resonant properties as is further discussed in the incorporated references and in particular in U.S. Published application number 2012-0038245.

As will be understood by those in the art, a variety of means of generating motion are thus adaptable for use in compressors according to the present invention. Examples include electric motors (both AC, DC, brushless, and with brushes), chemically fueled motors (including for example internal combustion engines), hydraulic or pneumatic motors, actuators (both mechanically amplified and otherwise), and even manual operation. Any such means of generating the desired transverse motion may be selected based on the constraints of the compressor application.

It will be apparent to those of ordinary skill in the art, the volume and rate of flow may be adjusted by adjusting the size of the compressor components (whereby larger pistons, chambers and ports allow for increased flow and smaller pistons, chambers and ports allow for decreased flow), changing the stroke length of the pistons (whereby longer stroke lengths create greater flow and lower stroke lengths create lesser flow), and/or by changing the pump speed (whereby faster speeds increase flow while lower speeds decrease flow). As will also be apparent, the tolerances may vary depending on the material to be compressed, with thicker gasses having larger molecular sizes allowing for looser tolerances than thinner gasses with small molecular sizes.

For all of the actuator-driven embodiments described, and embodiments utilizing actuated valves, it will be understood by those of skill in the art that a control mechanism, device or means (not illustrated) is necessary to ensure that the various actuators activate and deactivate at the proper times. Such means will be an electronic control circuit (not shown) of any of the suitable types known to those of ordinary skill in the art. Flow and back pressure sensors (not shown) may also be incorporated such that the control circuit can increase or decrease speed or volume as required to maintain a predetermined flow speed. While the specific control means will vary according to the type of actuator used, such means are well understood in the art for each type of applicable actuator. Additional information on controllers may be found in the incorporated references.

Other variations and embodiments will be apparent to those of ordinary skill in the art, all of which are within the scope of the present invention, which is limited only by the claims. 

1. A compressor comprising a glass cylinder having a hollow interior, a graphite piston within the glass cylinder, a connecting rod operably attached to the graphite piston, a cylinder head sealing one end of the glass cylinder and comprising an exhaust valve in operable connection with the hollow interior of the glass cylinder, and an inlet valve in operable connection with the hollow interior of the glass cylinder, wherein upon the connecting rod moving the graphite piston toward the cylinder head, material within the hollow interior of the glass cylinder is compressed until a sufficient pressure is attained to expel a portion of the material out the exhaust valve, and upon the connecting rod moving the graphite piston away from the cylinder head, material is drawn into the hollow interior of the glass cylinder through the inlet valve.
 2. The compressor of claim 1 wherein the inlet valve is mounted in the cylinder head.
 3. The compressor claim 1 further comprising a piston T-nut adapted to retain the graphite piston to the connecting rod.
 4. The compressor claim 3 wherein the inlet valve is mounted to the piston T-nut.
 5. The compressor of claim 1 wherein the inlet valve mounted to the graphite piston.
 6. The compressor of claim 1 further comprising a motor operably connected to the connecting rod such that operation of the motor causes the connecting rod to move the graphite piston transversely in the glass cylinder.
 7. The compressor of claim 1 further comprising an actuator operably connected to the connecting rod such that operation of the actuator causes the connecting rod to move the graphite piston transversely in the glass cylinder.
 8. The compressor of claim 1, further comprising a means of generating transverse motion of the graphite piston, wherein the motion generating means is operably attached to the connecting rod.
 9. The compressor of claim 8, wherein the motion generating means is a motor operably attached to an eccentric operably attached to the connecting rod
 10. The compressor of claim 9 wherein the motor is a brushless DC motor.
 11. The compressor of claim 8, wherein the motion generating means is a smart material actuator operably attached to the connecting rod whereby repeated activation of the actuator urges the piston in a first direction within the glass cylinder and deactivation of the actuator urges the piston in a second direction substantially opposite to the first direction within the glass cylinder.
 12. The compressor of claim 11 further comprising an electronic control circuit adapted to operate the smart material actuator at a resonant frequency.
 13. The compressor of claim 1, further comprising a low-friction ring adapted to mount on the graphite piston, whereby the ring provides a low-friction seal between the graphite piston and the inner walls of the glass cylinder.
 14. The compressor of claim 13, wherein the low-friction ring is formed of a synthetic resin.
 15. The compressor of claim 1 wherein the outside diameter of the graphite piston is substantially equal to the inside diameter of the glass cylinder.
 16. The compressor of claim 1, wherein the glass cylinder is formed of borosilicate glass.
 17. The compressor of claim 2 wherein the cylinder head further comprises a second inlet valve in operable connection with the hollow interior of the glass cylinder.
 18. The compressor of claim 1 in which the cylinder head further comprises a second exhaust valve in operable connection with the hollow interior of the glass cylinder.
 19. The compressor claim 1 wherein the inlet valve is a first reed valve and the exhaust valve is a second reed valve.
 20. A compressor comprising a glass cylinder having a hollow interior, a graphite piston within the glass cylinder, a connecting rod operably attached to the graphite piston, a cylinder head sealing one end of the glass cylinder and comprising an exhaust port in operable connection with the hollow interior of the glass cylinder, an inlet port in operable connection with the hollow interior of the glass cylinder, at least one inlet valve in operable connection with the inlet port, and at least one exhaust valve in operable connection with the outlet port, wherein upon the connecting rod moving the graphite piston toward the cylinder head, material within the hollow interior of the glass cylinder is compressed until a sufficient pressure is attained to expel a portion of the material out the exhaust valve, and upon the connecting rod moving the graphite piston away from the cylinder head, material is drawn into the hollow interior of the glass cylinder through the inlet valve. 